The first guide I've written for you is a little primer on how to understand debits and credits. Debits and credits are absolutely fundamental to financial accounting. If you don't understand this from the very beginning, you'll have a tough time in the class.
Read it and read it again. Read it until you can recite in your sleep which accounts are debited and which are credited. Then read it again.
On the scale of importance, understanding how to do journal entries is right behind understanding debits and credits. If debits and credits are the words of accounting, journal entries are the sentences.
It's pretty straightforward once you get the hang of it.
Bad Debt Expense and the Allowance for Bad Debts can be a little tricky to grasp, because there are a couple different ways to calculate it. I'll show you show an easy way to remember which method is which, and how to keep them separate.